Waste tank issues? 1969 Overlander

[edglenn]

I've got several qustions about the 1969 Overlander black tank:
The 1.5" black pipe from the kitchen sink and tub (passenger side) appears to circle around the rear of the trailer to the driver's side, and joins into the tank next to the toilet (I think). The sink drops directly into the tank, at the rear. However, when I look at the gate valve at the rear, I can just barely see a black 1.5" pipe which appears to join the gate valve assembly BETWEEN the gate valve a cover-cap. This appears to come from the driver's side. Is this a vent? It looks factory, but I can't tell if the tub and kitchen sink drain back into this pipe, too, which wouldn't make sense.
The reason I ask is I'm getting leakage below the gate valve, and when I pull the cap, there's liquid in there (which gushes out) when I test the kitchen sink. It seems to be coming from this mystery line.
I don't think the gate valve itself is leaking, however. It appears to be sealing fine.
After I tested the lines for the first time, there was a terrible odor for several days, so I obviously have either a tank leak, or a bad pipe joint.
I don't want to pull the tank unless I have to, of course.
Thanks!

[Inland RV Center, In]

Originally Posted by edglenn

I've got several qustions about the 1969 Overlander black tank:
The 1.5" black pipe from the kitchen sink and tub (passenger side) appears to circle around the rear of the trailer to the driver's side, and joins into the tank next to the toilet (I think). The sink drops directly into the tank, at the rear. However, when I look at the gate valve at the rear, I can just barely see a black 1.5" pipe which appears to join the gate valve assembly BETWEEN the gate valve a cover-cap. This appears to come from the driver's side. Is this a vent? It looks factory, but I can't tell if the tub and kitchen sink drain back into this pipe, too, which wouldn't make sense.
The reason I ask is I'm getting leakage below the gate valve, and when I pull the cap, there's liquid in there (which gushes out) when I test the kitchen sink. It seems to be coming from this mystery line.
I don't think the gate valve itself is leaking, however. It appears to be sealing fine.
After I tested the lines for the first time, there was a terrible odor for several days, so I obviously have either a tank leak, or a bad pipe joint.
I don't want to pull the tank unless I have to, of course.
Thanks!

Those old tanks were prone to cracking on the top.

Empty the tank and all it's contents.

Then drop in 2 to 4 ounces of food coloring.

Fill the tank with a garden hose, and see what happens.

The food coloring allows you to better locate the leak.

Andy

[edglenn]

Andy, thanks.
Will I need to remove a section of the bathroom floor to see the top of the tank? All I can see right now is the end of the gate valve, and none of the actual tank. I think I may be able to remove the toilet, and a section of the plywood floor. The PO had framed it up to raise the toilet, so I can cut out a section below the framing. As far as I can tell, the flange he used fits tight into the vertical tube feeding the tank. I don't think that's whats leaking, but I could be wrong on that.
Are these tanks repairable, and if so, what is used? Are they standard Polypropylene?

[Inland RV Center, In]

Originally Posted by edglenn

Andy, thanks.
Will I need to remove a section of the bathroom floor to see the top of the tank? All I can see right now is the end of the gate valve, and none of the actual tank. I think I may be able to remove the toilet, and a section of the plywood floor. The PO had framed it up to raise the toilet, so I can cut out a section below the framing. As far as I can tell, the flange he used fits tight into the vertical tube feeding the tank. I don't think that's whats leaking, but I could be wrong on that.
Are these tanks repairable, and if so, what is used? Are they standard Polypropylene?

How about a photo showing the floor flange, since that area was modified.

The old tanks were made with a junk plastic that simply dies in time, and crack.

Can it be repaired?

Yes, again and again and again.

Replacing it stops the headaches.

Andy

[JRookie]

The water from the tub and sinks don't drain into the tank, they drain outboard of the gate valve. If you have the cover cap on and use the sink, the water will back up in the piping, and when you remove the cap, it will come gushing out. This gray water will smell pretty bad too.

The first thing that tipped us off that our black tank was leaking was that the sheet metal box surrounding it had rusted through.